International Research Journal of Engineering and Technology (IRJET)
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Volume: 06 Issue: 01 | Jan 2019
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INVESTIGATION OF THE ELECTRICAL INDUCTION FURNACE USED FOR
ALUMINIUM RECYCLING
Gottmyers Melwyn J1, Dr. C. Bhagyanathan Ph. D2
1P.G
Student, M.E Manufacturing Engineering, Sri Ramakrishna Engineering College, Vattamalaipalayam,
Coimbatore-641022
2Associate Professor, Department of Mechanical Engineering, Sri Ramakrishna Engineering College,
Vattamalaipalayam, Coimbatore-641022
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Abstract - Aluminium had been extracted from the chief ore
furnaces in sizes ranging from 60-500 kw at frequencies
below thousand cycles and having pouring capacities of 2005000 lb of aluminium are available and are capable of
melting 5 to 7 lb per hour per kw rating of the furnace. Lowfrequency furnaces have a characteristic that they must be
started with a heel of molten metal, and so are emptied only
when cleaning is necessary. Since melting is rapid and no
combustion products are present, oxidation losses are at
minimum.
bauxite due to its abundance in nature, but the gas emissions
produced by the process has made researchers and
industrialists to look for alternatives. Since then the
aluminium has been reprocessed and have been accessible in
the secondary form with similar characteristics from its
antecedent. A lot of recycling methods have been followed, this
research work would give a detailed account of the induction
(electrical) method used to obtain secondary aluminium
alloys. To accomplish this machined aluminium scrap (He9)
alloy was melted in the induction furnace. The recycling
efficiency of the furnace, its performance compared to the
combustion process (coal, natural gas and oil) were also
closely analysed. The exertion also involved monitoring of the
energy ingestion of the induction furnace and the best furnace
that is appropriate for the industry was also determined
through the work.
2. LITERATURE SURVEY
Literature survey on evaluation of induction furnace and
the efficiency of aluminium recycling process along with the
process parameters are given in this section. The
requirement of furnace is to provide the required heating and
make sure no by-products are produced in the process. The
efficiency of the process plays a major role in any work
environment.
Key Words: Secondary aluminium, aluminium scrap (He9),
induction, energy consumption, process efficiency
William H. Macintosh gave a review on the recovery of
secondary aluminium and demonstrated that the Induction
furnaces offer several advantages over direct-fired furnaces:
low melt loss, good metal quality, and high efficiency. This
paper analyzes the advantages of using an induction furnace
for secondary aluminium recovery.
1. INTRODUCTION
The ore from which most aluminium is presently extracted,
bauxite, is a hydrated aluminium oxide. Aluminium is a good
electrical conductor; it is ductile and can be readily cast and
machined. Aluminium is the perfect ‘eco-metal’. Very little
aluminium is lost in the re-melting process. Increased
recovery, dismantling and sorting of spent products has led
to even greater recycling of aluminium is recycling becomes
increasingly important so does the life cycle of aluminium.
Along with the energy savings, recycling aluminium saves
around 95% of the greenhouse gas emissions compared to
the ‘primary’ production process. Recycled aluminium is a
valuable commodity, so most recycling centres will accept
your used scrap. Moreover, aluminium can be recycled
indefinitely with no limit on the number of times the metal
can be reused. According to the Aluminium Association, an
industry trade group, recycling just one can saves the
amount of energy it takes to watch the Super bowl in other
words, the amount of energy needed to power a television
for three hours. In recent years more extensive use is being
made of the induction furnace for melting of many
nonferrous alloys. High-frequency furnaces of the lift-coil
type are limited by crucible size to about 90-lb heats of
aluminium. Motor generator sets of 5 to 1000 kw providing
frequencies up to 10,000 cycles may be used. Low-frequency
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Vivek R. Gandhewar et al. gave a review on present
practices followed in Induction Furnaces. Through a
literature review account of various practices presently being
followed in steel industries using Induction Furnaces has
been carried out with a view to gather principal of working.
Apart from this a pilot study has also been carried out in few
industries in India. We provide some recommendations for
the productivity improvement. Due to non-availability of the
proper instrumentations the effect of the ill practices cannot
be precisely judged. If this is properly measured, the
percentage of productivity improvement in steel melting
Induction Furnace can be calculated. The review is carried
out from the literature in the various journals and manuals.
Angela O. Nieckele et al. analysed the factors that affect the
choice of liquid or gas fuel to be used in an industrial furnace
can be of extreme importance, having a direct effect on its
performance, on the level of pollutants emissions, and on the
equipment working life. These factors are highly dependent
on the combustion process and on factors such as the flame
shape and the temperature and heat flux distributions within
the furnace. In the present work, numerical simulations were
carried out, using the finite volume method, with the purpose
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International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 06 Issue: 01 | Jan 2019
p-ISSN: 2395-0072
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of analyzing and comparing the combustion process inside an
aluminium furnace when operating with two types of fuel: a
spray of liquid oil and a jet of natural gas, both reacting with
air. The results showed the possible damages that may be
caused by the combustion process if long or too intense and
concentrated flames are present, increasing the wall
temperatures and compromising the heat flux on the
aluminium surface.
aluminium will offer precise temperature controls in order
to achieve this goal
The charge is introduced into the furnace and the melting of
the aluminium scrap is done by the induction process,
melting of aluminium takes nearly 7500C and it is held at
that temperature for some more time for uniform melting.
Once this is completed the melt can be poured.
3. EXPERIMENTATION
3.4 POURING
3.1 SORTING
The molten metal is poured into the ingots specifically
preheated and coated with graphite. Preheating is done to
avoid the huge temperature difference between the cast and
the ingot as it might lead to certain casting defects. Graphite
coating is done for easy removal of the cast from the ingot.
Aluminium alloys are used in several sectors and
applications in combination with a lot of different materials,
such as metals (steel, copper, zinc) or, in other cases, rubber,
plastic, and glass. The Al scrap inevitably contains residuals
of such materials that oblige refiners to properly screen the
scrap before melting to enhance recycling efficiency and
reduce the presence of impure elements. Undesired particles
and elements may be reduced during the melting by refining
processes, but this is challenging due to thermodynamic
barriers. The physical separation (sorting) of solid scrap
streams is a reliable solution to prevent the commingling of
metals and elements, even if the technical benefits are not
completely evident.
3.5 HOURLY ANALYSIS
Two 80kg aluminium scraps were melted separately and
during the melting period in the induction furnace every
hour the parameters were noted down; this is done to
monitor the melting process keeping the process parameters
at stake. The parameters noted down each hour would be
the temperature of the materials inside the furnace and the
energy rating along with the state of the metal. The
temperature is measured using the thermocouple since there
may be variations in the display. Meanwhile the energy
rating is noted from the display.
Different types of scrap require various sorting methods and
different results can be obtained. Thus, it is necessary to
understand when the benefits outweigh the required
investment. Sorting casting and wrought Al alloys, for
instance, allows the production of high quality wrought
alloys that are actually not possible with mixed scrap,
however, sorting technologies for this issue have high capital
investments and high running costs.
3.6 LOAD VARIATION
In order to determine the efficiency of the process, the
furnace was loaded with scraps ranging in weight from 30kg
to 80kg in steps of 10kgs at a time this was done to
determine the efficiency of the process at various loads. The
yield obtained in the various processes have to be
determined.
The sorting technologies normally used for Al recycling aim
to separate aluminium scrap from other materials, such as
other metals or rubber. The research and the innovative
technologies are now oriented not only to separate Al scrap,
but to recognize the alloy group and, if possible, the specific
Al alloy.
4. RESULT AND DISCUSSION
4.1 CHEMICAL ANALYSIS
3.2 PREHEATING OF THE SCRAP
Table 1: Chemical Composition
Pre-heat oven is used to pre-heat scrap before it is added to
the furnace. The heat comes from the recuperator and does
not require the use of additional gas. Pre-heating is done to
remove water from the scrap. The presence of water when
the metal is placed in the furnace will cause an explosion as
the water rapidly vaporizes.
3.3 MELTING IN THE INDUCTION FURNACE
CAST
BEFORE
MELTING
IN THE
FURNACE
AFTER
MELTING
IN THE
FURNACE
An induction melting furnace for aluminium is designed
specifically for the purpose of melting lower density metal,
employing exactly the right temperatures and evenly
distributing the heat. This is vital in melting such metals as
aluminium if you want to preserve the expected lifetime of
aluminium and its quality. The ideal melting furnace for
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Si%
Cu%
Fe%
Mg%
Mn%
Ti%
Al%
98.85
.60
0.008
0.05
.45
.02
.01
98.7
.55
.005
.22
.40
.02
.01
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Volume: 06 Issue: 01 | Jan 2019
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Sample material is evaporated by spark discharge inside the
instrument. In this process, the released atoms and ions are
excited and emit light. This light is directed into the optical
systems and measured using CCD* technology. Calibration
data are already stored in the instrument's memory. The
measured values are compared with these data. The
measured values are converted into concentrations and then
displayed on the screen.
Q = 2700 x 0.08792 (0.9(660 -28) + 398 + 0.9 (800-660))
Q = 237.4((0.9x 630) + 398 + (0.9 x 140)) = 900 MJ
4.2 HOURLY ANALYSIS
The melting time is calculated as follows:
This was done to determine the energy rating of the process
Efficiency Calculation
Input Power available = 22 kW
Power consumption for Ingots = 238 kWh/ton
Thus, Melting Time
= (238/22) *x 1 hour = 10.81 hours
Thus, for melting 100kg of aluminium scrap, it requires
10.81 hours. The melting time varies from scrap to scrap.
4.4 MELTING TIME CALCULATION
The melting time matters a lot as, during this period,
induction furnace draws heavy current from the supply
mains and inject harmonics into the system.
For Melt of 80 Kg of LM-25
Table 2: Hourly Analysis for Energy Consumed
4.5 COMPARISON STUDY
Time
(Hrs.)
0
1
2
3
4
Temperature
(*C)
26
329
423
524
628
Input (kWh)
Observation
5574.4
5601.8
5628.4
5654.7
5683
5
6
7
8
680
756
784
743
Total Energy
spent
Avg. Energy
/ Hrs.
5710.4
5737.1
5755.5
5755.5
181.1
Solid
Solid
Solid
Solid
SemiSolid/Next50%
addition
Semi-Solid
Melt
Melt/ Pour
Offline/Pour
As mentioned earlier various industrial analysis were made
and the procedures followed in the industries were analysed
the yield and energy required to produce 100kg melt was
studied in brief and a comparison was drawn between those
industries and the induction furnace for melting aluminium.
The energy calculations for other methods were done by
converting it into kwh.
The amount of fuel burnt multiplied by the calorific value of
fuel multiplied by a factor of 1.02246 (considering
atmospheric conditions) and these three divided by 3.6
Gas units to kwh
(Fuel burnt*1.02246*CV of fuel)/3.6
Calorific value of LPG: 27 MJ/kg
Fuel required to melt 100 kg Aluminium: 40 m3
: (40*27*1.02264)/3.6
= 306 kwh
Therefore 306 kwh of energy is spent using coal as fuel to
melt 100kg of aluminium
25.87142857
As shown in the table the average amount of energy required
per hour is 25kw
The yield obtained by melting 80kg aluminium scrap was
76kg
Table 3: Yield and Energy Consumed
Melting
Type
INDUCTION
(ELECTRIC)
LPG
Furnace oil
Coal
gas
4.3 SPECIFIC ENERGY CONSUMPTION
181kwh energy is used to produce 76 kg of aluminium ingot
Therefore, Specific Energy Consumption =181/76
= 2.381kwh
Quantity of Heat required to melt the Charge
Melting point of aluminium is about 660oC at standard
atmospheric conditions. Thus in order to obtain enough
fluidity, choose pouring point of aluminium, Tp =8000C.
Q = 𝜌v (Ca (Ta– To) + hfo+ Ca (Tp – Ta))
Where, Density of aluminium, 𝜌 = 2700kg/m3
, Volume of material V = 0.08792m3
Specific heat of aluminium, Ca = 0.9kJ/kg0C,
Melting point of aluminium, Ta = 660oC
Latent heat of fusion of aluminium hfo= 398kj/kg;
Atmospheric Temperature to = 280C
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Yield
95%
Energy required
(kwh)
238
90%
93%
88%
85%
390
190
306
326
The tabulation shows that the electric (induction) heating is
a better process than other types as the yield is high for
induction furnace consuming lesser energy than other
processes.
4.6 LOAD VARIATION
Aluminium scraps were added in the following weight
measures separately 30kg, 50kg, 80kg and 100kg this was
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done to determine the efficiency of the process when
subjected to different loads of aluminium scrap the results of
the same are tabulated here.
liquid fuel. Applied Thermal Engineering, 31(5),
pp.841- 851.
4) Dey, A.K., 2018, January. Energy Efficiency Model for
Induction Furnace. In IOP Conference Series:
Materials Science and Engineering (Vol. 302, No. 1,
p. 012047). IOP Publishing.
5) Karawatthanaworrakul, S., Tongthavornsuwan, S.
and Tangwarodomnukun, V., 2015. Efficiency
Improvement of Aluminium Recycling Process. The
Journal of Industrial Technology, 11(2), pp.56-68.
6) Mbuya, T.O., Odera, B.O., Ng'ang, S.P. and Oduori,
F.M., 2011. Effective recycling of cast aluminium
alloys for small foundries. Journal of Agriculture,
Science and Technology, 12(2).
5. CONCLUSIONS
Electrical energy is found to be an advantageous method to
melt the aluminium alloys for production of secondary
aluminium scrap. The results clearly show that the amount
of aluminium yield obtained is comparatively higher than the
process where combustion of fuels (coal, natural gas, oil and
petrol) is carried out.
7) Zeru, G.T., 2015. Development of recycle-friendly
secondary cast aluminium alloy for cylinder head
applications (Doctoral dissertation).
8) Xu, J.L., Zhang, J., Shi, Z.N., Gao, B.L., Wang, Z.W. and
Hu, X.W., 2014. Current efficiency of recycling
aluminium from aluminium scraps by electrolysis.
Transactions of Nonferrous Metals Society of China,
24(1), pp.250-256.
One of the main reason for the electric process is that the
melting of the material is carried out by the process of
induction, in case of combustion there is always a loss due to
the reactions of the elements in the melt with the fuel and
escape in the form of combustion by-products.
9) Verran, G.O. and Kurzawa, U., 2008. An
experimental study of aluminium can be recycling
using fusion in induction furnace. Resources,
Conservation and
Recycling, 52(5), pp.731736.
In industry point of view when the energy
consumption is less the particular industry or organization
would enjoy a lot of benefits in the form of saving the
expenditure for fuel and the same can be used for other
miscellaneous costs or overhead costs that occur in the
industry.
The most important factor is that
environment friendly process. Almost all mechanical process
cause pollution to a higher level but by consuming less
energy a lot of benefits can be sought by the industry.
10) Arkin, T. and Hassan, M.I., 2017. Metal Scrap
Preheating using Flue Gas Waste Heat. Energy
Procedia, 105, pp.4788-4795.
11) Duflou, J.R., Tekkaya, A.E., Haase, M., Welo, T.,
Vanmeensel, K., Kellens, K., Dewulf, W. and
Paraskevas, D., 2015. Environmental assessment of
solid state recycling routes for aluminium alloys:
can
solid state processes significantly reduce
the environmental impact of aluminium recycling?
CIRP Annals, 64(1), pp.37-40.
ACKNOWLEDGEMET
We would like to thank our Head of the Department Dr.P.
Karuppuswamy for his support and the College for helping
us to carry out the research works in the premises
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